The present invention relates to an electronic circuit board and a soldering method therefor and, more particularly, to a technique for preventing an inter-terminal solder bridge formed in a flow soldering process for an electronic circuit board.
To solder various types of component terminals and board wires of a conventional electronic circuit board to each other by a flow soldering method, components are temporarily fixed with an adhesive to corresponding component terminal soldering lands formed at predetermined portions on the board. Alternatively, the components are inserted in component insertion holes formed in the lands, are dipped in a molten solder jetting upward from a flow solder tank, and are passed through the molten solder at a predetermined speed.
It is known that when the terminal pitches of the component to be soldered are small, an inter-terminal bridge tends to form between the terminals of the component due to excessive solder. To remove the excessive solder on a board 102 having a periphery where components are to be mounted as shown in FIG. 3A, an extending land 106 as shown in FIG. 3B is formed most downstream of circular lands 105 on each connector 101 mounted along the arrow D of the flow solder conveyance direction. Such an extending land serves as a so-called excessive solder absorption land, which prevents a component inter-terminal bridge from being formed by the surface tension of the solder on the land that is removed from the solder tank.
Alternatively, the land at the terminal end of a component where an inter-terminal bridge tends to be formed is enlarged in a direction (to be referred to as a board flow direction D hereinafter) along which the component is passed above the molten solder and which is opposite to the flow direction.
With the conventional techniques described above, when a component having a small terminal pitch is to be arranged such that its terminal array direction along which the terminals of the component are aligned is perpendicular to the board flow direction, a solder bridge between the terminals is not prevented sufficiently, and solder bridges tend to form. It is also known that the board warps on its component mounting surface side due to thermal expansion caused by the heat of the molten solder. This also makes it difficult to prevent a component inter-terminal bridge from being formed by the surface tension of the solder on the land that is removed from the solder tank.
The present invention has therefore been made in view of the problems described above, and has as its object to provide an electronic circuit board which can solve a soldering error for a component arranged such that its terminal array is perpendicular to the convey direction of the electronic circuit board which is to be flow-soldered, and a soldering method therefor.
In order to solve the problems described above and to achieve the above object, according to the present invention, there is provided an electronic circuit board having a land formed on a flow soldering surface thereof for flow soldering, characterized by comprising an extending land formed to be substantially perpendicular to a convey direction for the flow soldering and to extend toward a downstream side of warp of the board.
The present invention is also characterized in that the extending land is formed for soldering a terminal of a multi-terminal component including a connector, at one portion on the downstream side of the warp.
The present invention is also characterized in that the warp is formed by thermal expansion that takes place during the flow soldering.
There is also provided a soldering method for an electronic circuit board having a land formed on a flow soldering surface thereof for flow soldering, characterized in that an electronic component is mounted on an electronic component mounting surface of a board having an extending land which is formed to be substantially perpendicular to a convey direction for the flow soldering and to extend toward a downstream side of warp of the board, and a molten solder is brought into contact with a lower surface of the electronic component mounting surface while conveying the board in the convey direction, thereby performing flow soldering. The present invention is also characterized in that the extending land is formed at one portion on the downstream side of the warp, and the flow soldering is performed after a terminal of a multi-terminal component including a connector is inserted in the extending land.
The present invention is characterized in that the warp is formed by thermal expansion that takes place during the flow soldering.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.